An internal cap member intended to be placed on the container. The internal cap member carries a security ring including a security element including a locking abutment mobile radially between a cooperation position, favored by elastic biasing, in which the locking abutment cooperates with a complementary locking abutment carried by the container, and a separation position, in which the locking abutment is separated from the complementary locking abutment. The security ring is mobile axially on the cap. The closure device also includes an element for transforming the axial movement of the security ring into radial movement of the security element, making it possible for the radial position of the locking abutment to change from its cooperation position to its separation position.
